In the pharmaceutical art water-soluble active ingredients are conventionally formulated together with insoluble excipients in an attempt to maximize their dissolution rate. One such non water soluble pharmaceutical excipient which is widely used is microcrystalline cellulose. Microcrystalline cellulose is particularly useful in the formation of spheroids by spheronization and can itself be processed to give spheroids by simple granulation with water followed by extrusion and spheronization. In general, the greater the proportion of microcrystalline cellulose present in a pharmaceutical composition, the easier it is to form spheroids.
Microcrystalline cellulose as an excipient generally exercises little control over the release of active ingredient from a dosage form and it would therefore be expected that compositions containing a high proportion of microcrystalline cellulose would show normal release characteristics.
A normal release pharmaceutical preparation is one that achieves fast release of active ingredient in a short period of time. Conventionally a dissolution rate of 90% or more in 45 minutes would be acceptable to constitute a normal release preparation.